Most of the liquid crystal display devices that provide color display include sets of color filters for transmitting red (R), green (G), and blue (B) light therethrough, such that one set is provided for every three subpixels into which one pixel is divided. However, about ⅔ of backlight irradiated on a liquid crystal panel is absorbed by the color filters, and therefore liquid crystal display devices using color filters have a problem of low light-use efficiency. Accordingly, attention is focused on field-sequential liquid crystal display devices which provide color display without using color filters.
In the field-sequential system, a display period for one screen (one frame period) is divided into three subframe periods. In the first subframe period, a red component of an input signal is inputted to display a red screen, in the second subframe period, a green component is inputted to display a green screen, and in the third subframe period, a blue component is inputted to display a blue screen, so that a color image is displayed on the liquid crystal panel. In this manner, field-sequential liquid crystal display devices can dispense with color filters and therefore have about three times the light-use efficiency of liquid crystal display devices using color filters.
Japanese Laid-Open Patent Publication No. 2006-235443 describes a liquid crystal display device in which color signals included in input signals are distributed to subframes of base colors and complementary colors, such that differences in tone between the subframes are rendered small while maintaining colors expected from input signals of the base colors alone. To take advantage of the response speed of the liquid crystal being proportional to differences in tone, this liquid crystal display device renders differences in tone small between subframes to minimize color shifts between images. Specifically, when there are three base colors, red, green, and blue, colors in an image are distributed to subframes for red, green, blue, and complementary colors thereof, i.e., six colors in total, in accordance with predetermined equations. At this time, a color distribution ratio is obtained such that the sum of the absolute values of differences in tone between adjacent subframes is minimized while maintaining colors expected from input signals of the base colors alone. Color signals are distributed to the subframes on the basis of the color distribution ratio thus obtained, thereby rendering the differences in tone small between the subframes. As a result, the response speed of the liquid crystal becomes faster than in the case where the differences in tone are large, so that the color shifts between images can be minimized.
Patent Document 1: Japanese Laid-Open Patent Publication No. 2006-235443